Putting the salmon into salmonberry

Published on
December 3, 2018

Salmonberry (Rubus spectabilis) is a common understory shrub in British Columbia’s coastal forests, named for the color of its tasty berries. In this study several labs in the Biological Sciences department and visiting M.Sc. student Gregory van de Top collaborated to collect and measure salmonberry plants on the remote central coast of British Columbia. Here, salmon runs in the many small rivers and streams provide an important source of nutrients, as bears, wolves, eagles and other predators transport salmon carcasses into the adjacent forests. The study asked whether salmonberry leaves have more ‘stomata’ along streams with more salmon.

‘Stomata’ are microscopic pores in leaves, typically numbering hundreds per square millimeter. Stomata capture the carbon dioxide needed for photosynthesis, and by evaporating water transport nutrients from the root system through the vascular system to the leaves. Stomatal density is flexible: for example, in many species it is higher on mountains due to the lower availability of carbon dioxide at altitude. We found that the density of salmonberry stomata increased in direct relationship to the density of spawning salmon, varying by more than 20% over the range of salmon densities observed. We interpret this to mean that extra stomata are advantageous on streams with larger salmon runs, as this enables the capture of more nutrients, especially nitrogen, otherwise in short supply in these nutrient-poor rainforests. Though precipitation is high (>3000 mm per year), water is not unlimited and even here, plants must adjust stomatal density to balance the inherent trade-off between water loss and photosynthetic gain. The name ’salmonberry’ is apt not only for the color of the berries, but for the ability of this plant to capture hard-to-come-by nutrients in these temperate rainforests.

van den Top GG, Reynolds JD, Prins HHT, Mattsson J, Green DJ, Ydenberg RC (2018) From salmon to salmonberry: The effects of salmon-derived nutrients on the stomatal density of leaves of the nitriphilic shrub Rubus spectabilis. Functional Ecology 32(11): 2625-2633.